Method for depositing a thin layer and product thus obtained

[0001] The invention relates to the field of inorganic thin layers, especially applied to glass substrates. More specifically, it relates to a method for at least partially crystallizing said thin layers and certain products obtained by this method.

[0002] Many thin layers are applied to substrates, especially flat or slightly convex glass, in order to give the obtained materials special properties: optical properties, e.g. reflection or absorption, radiation in a given wavelength range, specific electrical conductivity properties or related properties facilitating purification or the ability of the material to self-clean.

[0003] These thin layers are most often based on inorganic compounds: oxides, nitrides or metals. Their thickness generally differs from a few nanometers to several hundred nanometers, hence their term "thin".

[0004] Thin layers based on metallic silver, which have properties of electrical conductivity and reflection of infrared radiation, which are used in glazing with solar radiation control, especially sunscreen (aimed at reducing the amount of incoming solar energy) or with low emissivity (to reduce the amount of energy discharged outside the building or vehicle).

[0005] Silver-based layers have the special feature that they can be seen to improve some of their properties when they are in an at least partially crystallized state. Generally, the maximum increase in the degree of crystallinity of these layers (mass or volume fraction of the crystallized substance) and the size of the crystal grains (or the size of coherent diffraction domains measured by X-ray diffraction methods) and even, in some cases, favoring a specific crystallographic form are sought.

[0006] It is known that silver layers having a higher degree of crystallinity and consequently a low residual content of amorphous silver have lower emissivity and resistivity than layers of mainly amorphous silver. Therefore, the properties of electrical conductivity and low emissivity of these layers are improved.

[0007] A method of applying thin layers, especially on a glass substrate, which is widely used on an industrial scale, is a method of cathodic sputtering assisted by a magnetic field called the "magnetron" method. In this method, the plasma is generated under high vacuum near the target containing the chemical elements to be applied. Active plasma particles, by bombarding the shield, tear out the elements that settle on the substrate and form the desired thin layer. This method is referred to as "reactive" when the layer consists of material formed as a result of a chemical reaction between elements removed from the target and the gas contained in the plasma. The main advantage of this method lies in the possibility of applying on the same line a very complex system of layers, by causing the gradual passage of the substrate under different discs, generally in one and the same device.

[0008] During the industrial use of the magnetron process, the substrate remains at ambient temperature or undergoes a moderate increase in temperature (below 80 ° C), especially when the substrate's transition speed is high (which is generally desirable for economic reasons). This may be an advantage, however, in the case of the above-mentioned layers it is an inconvenience, because the low temperatures used usually do not allow sufficient crystal growth. This is especially the case for thin layers of small thickness and / or layers made of materials whose melting point is very high. Thus, the layers obtained according to this method are mainly or even completely amorphous or nanocrystalline (where the average crystal grain size is below a few nanometers) and it has been found that thermal treatments are necessary to obtain the desired degree of crystallinity or the desired grain size.

[0009] Possible thermal treatments consist of reheating the substrate, either during or after application, at the exit of the magnetron line. More generally, temperatures of at least 200 ° C or 300 ° C are necessary. In fact, the crystallization is the better, and the grain size the larger the closer the substrate temperature is to the melting point of the thin film forming material.

[0010] The heating of the substrate on industrial magnetron lines (during application) has proved difficult to implement, in particular, since the heat transfer under vacuum, which is necessarily of the nature of radiation, is difficult to control and causes high costs for substrates of large order sizes a few meters wide. For thin glass substrates, this type of treatment often has a high risk of cracking.

[0011] Heating the coated substrate after application, for example, by placing the substrate in an oven or dryer, or subjecting the substrate to infrared radiation from conventional heating devices, such as lamps emitting infrared radiation, also has drawbacks, as these various methods contribute to heating without distinguishing between the substrate and the thin layer. Heating the substrate to temperatures above 150 ° C can cause cracks in large sized substrates (several meters wide), because it is impossible to ensure identical temperature across the entire width of the substrate. In addition, heating the substrates slows down the entire process because it is necessary to wait for them to cool completely before considering cutting or storing them, which generally involves laying the substrates one on top of the other. Very carefully controlled cooling is also necessary in order to avoid stress generation in the glass and thus the possibility of cracking. Because very carefully controlled cooling is very expensive, usually annealing is not controlled enough to eliminate thermal stress in the glass, which increases the number of cracks in the line. Annealing also has the disadvantage of making glass cutting more difficult, with cracks having a less strong tendency for linear propagation.

[0012] The heating of the substrates takes place when the glass is bent and / or toughened because the glass is reheated above its softening point (generally above 600 ° C and even 700 ° C in a few minutes). Thus, quenching or bending enables the desired crystallization result of thin layers to be obtained. However, it would be costly to subject all glazing to such treatments only to improve the crystallization of the layers. In addition, toughened panes cannot be cut more and some thin film systems cannot withstand the high temperatures they are exposed to when toughening glass. An example of this type of heat treatment is given in US 2004/0005467.

[0013] The invention aims to propose a method that allows the crystallization properties of thin silver-based layers to be improved, but without the above-mentioned disadvantages.

[0014] To this end, the invention relates to a method for treating at least one continuous silver-based thin layer applied to a first surface of a substrate, wherein each point of said at least one thin layer is brought to a temperature of at least 300 ° C while maintaining the temperature less than or equal to 150 ° C at any point on the surface of said substrate opposite to said first surface, so as to increase the degree of crystallinity of said thin layer, while maintaining its continuity and without the melting step of said thin layer.

[0015] In the sense of the present invention, "thin continuous layer" is meant that the layer covers substantially all of the substrate or, in the case of an arrangement of layers, all of the underlying layer. It is important that the continuous nature of the thin layer (and thus its favorable properties) be maintained during the treatment according to the invention.

[0016] By "layer point", is meant a layer zone being processed at a given moment. According to the invention, the entire layer (and hence each point) is brought to a temperature of at least 300 ° C, but each point of the layer is not necessarily processed simultaneously. The layer can be processed in its entirety at the same time, with each point of the layer being simultaneously brought to a temperature of at least 300 ° C. Alternatively, the layer may be treated in such a way that various points or sets of layer points will be successively brought to a temperature of at least 300 ° C, the latter being more commonly used for continuous industrial scale use.

[0017] The method of the invention allows the supply of energy sufficient to promote crystallization of the thin layer through a physicochemical mechanism of crystal growth around embryos that are already present in the layer while remaining in the solid phase. The method of the invention does not use a crystallization mechanism by cooling the molten material, on the one hand, because this would require bringing the thin layer to extremely high temperatures to achieve its melting, and on the other hand, because it may lead to changes in the thickness and / or refractive indexes of the layers thus changing their properties. In particular, this would change their optical appearance causing unevenness visible to the naked eye.

[0018] The method of the invention has the advantage of heating only a thin layer (or thin layers in the case of a layer system) without significant heating of the entire substrate. Thus, it is no longer necessary to carry out long-term and controlled cooling of the substrate before cutting or storing glass. This method also makes it possible to integrate the heating device on existing continuous production lines, more particularly in the space between the exit from the vacuum application chamber of the magnetron line and the device for storing glass. In some cases it is also possible to carry out the treatment according to the invention in the vacuum deposition chamber itself.

[0019] In an industrial application integrated with a magnetron line, the method is generally continuous in the sense that the substrate moves and thus undergoes linear motion in the X direction. Thus, each point of the thin layer is preferably treated according to one of the following methods: either the heating means are solid and one can simultaneously process a set of points forming a line in the Y direction perpendicular to the X direction, or the heating means are movable in the Y direction and each point processed successively. The method according to the invention can be carried out on a ground placed both horizontally and vertically. It can also be carried out on a substrate comprising thin layers on its two surfaces, wherein at least one layer of one surface or each surface is treated according to the invention. In the case where thin layers applied to two surfaces of the substrate are treated according to the invention, it is possible to perform the simultaneous or successive treatment of said thin layers of each surface with identical or different techniques, especially depending on whether the nature of the layers to be treated is identical or different. The case in which the treatment according to the invention is carried out simultaneously on two surfaces of the substrate therefore falls within the scope of the invention.

[0020] It is not physically possible to heat the layer without heating the substrate, because increasing the temperature in the layer, due to thermal conductivity mechanisms, will necessarily cause heating of the substrate zone of the closest layer, and thus a high temperature gradient over the thickness of the substrate. Such large thermal gradients, sometimes called thermal shocks, are known to systematically cause cracks in sodium-calcium-silicate glasses commonly used in the flat glass industry. These cracks, which are caused by the varied thermal expansion between different glass zones subjected to different temperatures, are more easily formed in the case of silicate-soda-lime glasses, because their expansion coefficient is quite high. In addition, they are more easily formed for large-sized substrates (at least 1 m, even 2 or even 3 m in length) because it is more difficult to ensure high temperature uniformity for large substrates.

[0021] However, the inventors have shown that heat treatment using only moderate and controlled heating of a limited substrate zone allows freeing from this cracking problem, which until now has been considered unavoidable. Thus, during the implementation of the present invention, it is necessary that the temperature of the surface of the substrate opposite to the surface on which the thin layer being treated is not higher than 150 ° C. This feature is obtained by choosing a heating method specially adapted for heating a thin layer rather than a substrate and by controlling the time or intensity of heating and / or other parameters depending on the heating method used, as described in more detail in the text below.

[0022] A common feature of all the heating methods that can be used according to the invention lies in the fact that they allow the generation of very high power per unit area, which, however, cannot be quantified in absolute terms because it depends on many factors, including the nature and thickness layer. This high power per unit area enables the desired temperature to be reached extremely quickly at the layer level (generally in less than or equal to 1 second) and, consequently, to reduce the duration of the treatment. The heat generated does not have time to diffuse into the substrate. Each point of the thin layer is treated according to the invention (i.e. brought to a temperature greater than or equal to 300 ° C) for a period generally less than or equal to 1 second, or even 0.5 seconds. In contrast, since conventionally used infrared lamps do not allow these high powers per unit area to be achieved, the processing time must be longer (often several seconds) to achieve the desired temperatures, and the substrate is then necessarily brought to high temperatures by heat diffusion even if the wavelength of the radiation is adjusted so that it is absorbed by the thin layer and not by the substrate.

[0023] In order to maximally limit the number of cracks for the largest substrates (e.g. 6 meters long by 3 meters wide), it is preferable to maintain a temperature lower than or equal to 100 ° C, especially 50 ° C throughout the entire treatment, at any point of the substrate surface opposite to the surface on which the thin layer is applied.

[0024] Another advantage of the invention is that the thin layer or thin layer system is subjected to quenching equivalent. It happens that some thin film systems have modified optical properties (colorimetric coordinates, light or energy transmission) when the glass is toughened. Therefore, the method of the invention makes it possible to obtain non-toughened glass (and thus not having a stress profile specific to toughened glass, which makes it suitable for cutting), but having essentially the same optical properties as it would be toughened.

[0025] The degree of crystallization obtained by the process according to the invention is preferably greater than or equal to 20% or 50%, especially 70% and even 90%. This degree of crystallization, defined as being the mass of the crystallized material in relation to the total mass of the material, can be determined by X-ray diffraction using the Rietveld method. Due to the mechanism of crystallization by the growth of crystalline grains from embryos or nuclei, an increase in the degree of crystallization is usually accompanied by an increase in the size of the crystalline grains or coherent diffraction domains measured by X-ray diffraction.

[0026] The substrate is preferably transparent, glass, especially sodium silicate. It can also be made of a plastic material such as polycarbonate or polymethyl methacrylate. Preferably, it has at least one dimension greater than or equal to 1 m, even 2 m, and even 3 m. The thickness of the substrate generally varies between 0.5 mm and 19 mm, the method according to the invention being particularly advantageous for the thinnest substrates whose thickness is less than or equal to 4 mm or even 2 mm.

[0027] The thin layer is a silver-based layer. Even more preferably it consists of such metal. The thickness of the thin layer is preferably between 2 and 500 nm.

[0028] These layers have the special feature of being completely transparent to UV-Vis radiation (with absorption below 50% in the visible range). Because their absorption spectrum is slightly different from the absorption spectrum of the substrate (especially in the case where the latter is glass), it is particularly difficult to specifically heat the layer rather than the substrate. Other layers, such as silicon, have strong visible and near-infrared absorption, which facilitates their selective heating, for example when converting amorphous silicon into polycrystalline silicon.

[0029] The thin layer treated according to the invention may be the only thin layer applied to the substrate. It may also be contained in a thin layer system comprising thin layers usually selected from oxides, nitrides or metals. The thin layer can also be a thin layer system in itself. In the case where the thin layer to be treated is contained in a thin layer system, the method of the invention can improve the crystalline properties of one or more thin layers of the system.

[0030] A thin silver or silver based layer is preferably included in the layer system, in particular to avoid oxidation. For solar controlled or low emissivity glazing, a thin silver-based layer is usually applied between two thin dielectric layers based on oxide or nitride. Under the silver layer, a very thin layer may also be applied to support the wetting and nucleation of silver (e.g. from ZnO zinc oxide) and, above the silver layer, a second very thin layer (protective, e.g. from titanium) to protect the silver layer when applying the next layer is carried out in an oxidizing atmosphere or in the case of thermal treatments leading to oxygen migration to the system. Layer systems may also contain several silver layers, each of these layers generally being influenced by the inventive method. In the case where the system includes a zinc oxide layer, the treatment of the silver layer is usually also accompanied by an increase in the degree of crystallization of zinc oxide.

[0031] The thin layer prior to the treatment according to the invention can be obtained by any type of process, in particular by methods for producing mainly amorphous or nano-crystalline layers, such as the magnetron process, plasma assisted chemical vapor deposition (PECVD) method, evaporation method under vacuum or sol-gel method. Preferably, however, it is a "dry" layer, containing no aqueous or organic solvent, in contrast to the "wet" layer, for example, obtained by the sol-gel method. More preferably, it is obtained by sputtering, especially in a magnetic field (magnetron process). In the case of a sol-gel obtained layer, the precursors in solution (sol) are applied to the substrate, the resulting layer must then be dried and annealed to eliminate all traces of solvent. Thus, in this case, the energy supplied by heating is primarily used to eliminate this solvent without necessarily affecting the crystallization properties of the layer, and as a consequence it is more difficult to improve said properties in a sufficiently short time so as not to heat the substrate as well.

[0032] To facilitate, the heating of the layer is preferably carried out under air and / or atmospheric pressure conditions. Some heating methods, however, are compatible with vacuum, and it may be advantageous to carry out heating of the layer in the vacuum application chamber itself, e.g. before subsequent application.

[0033] Various heating means allow the method of the invention to be used, enabling the generation of very high power per unit area. Heating parameters such as the power of heating means or heating time are in each case adjusted by a specialist in the field, depending on various parameters such as the type of heating method, thickness or type of layer, size and thickness of the substrates to be treated, etc.

[0034] When the thin layer is electrically conductive (as is the case with silver), heating of the thin layer can be accomplished by induction.

[0035] Heating by induction of metal parts is a well known method of achieving high temperatures in a fast and controlled manner in mass conductive parts (steel reinforcement, zonal silicon melting). The main applications relate to the fields of agri-food (boiler heating, baking flat products on metal strips, extrusion baking) and metal production (melting, heating before molding, mass heat treatment, surface thermal treatment, coating treatment, welding, soldering).

[0036] The alternating current flowing through the coil (called a solenoid or coil) generates a magnetic field in it oscillating at the same frequency. If the electrically conductive part is placed inside the coil (or solenoid), currents induced by the magnetic field are generated and heat this part by the Joule effect.

[0037] Currents appear on the surface of the part to be heated. You can define a characteristic depth called the thickness of the skin, giving in the first approximation the thickness of the current layer. The thickness of the skin currents depends on the type of metal being heated and decreases as the frequency of the current increases.

[0038] For heating an insulating substrate covered with a conductive layer, it is preferred to use high frequency polarization to concentrate the effect of the inductor on the surface portion of the material. The frequency is preferably between 500 kHz and 5 MHz, especially between 1 MHz and 3 MHz. Preferably an inductor specially adapted for processing flat surfaces is used.

[0039] Induction is not preferred when the thin layer is less than 20 nm thick, or even less than 10 nm thick. For these particularly thin layers, very high frequency is needed, and because the volume of the layer is very low, the machining efficiency is weakened.

[0040] When the thin layer absorbs at least part of the infrared radiation, heating of the thin layer can be carried out by means of radiation whose wavelength is contained in said part of the infrared radiation absorbed by said layer. In order to maximally limit heat supply to the substrate, the selected radiation wavelength is preferably not included in the part of the infrared radiation absorbed by the substrate. For the above-mentioned reasons, radiation must have high power per unit area. For this reason, the heating of the thin layer is preferably carried out by means of an infrared laser. Lamp systems emitting infrared radiation connected to a concentrating device enabling high power per unit area to be achieved are also applicable.

[0041] For the silver-based layer, it is preferable to use a laser emitting radiation whose wavelength is between 0.5 and 5 microns. The YAG laser (yttrium-aluminum-garnet Y2Al15O2) with an admixture of neodymium, emitting continuously or pulsed radiation with a wavelength of about 1 micrometer, proved to be particularly well adapted, especially if the substrate does not absorb in this wavelength range, as is the case colorless glass with an iron oxide mass content of 0,1% or less.

[0042] To increase ease of implementation, the lasers used within the scope of the invention may be fiber optic, which means that the laser radiation is injected into the optical fiber and then delivered close to the surface to be treated by the focusing head. The laser can also be optical fiber in the sense that the reinforcing medium is in itself an optical fiber.

[0043] Since lasers can only illuminate a small area (usually of the order of one fraction from mm to several hundred mm), in order to treat the entire surface it is necessary to provide a laser beam displacement system in the ground plane or a system creating a linear laser beam that simultaneously exposes the entire width of the ground , under which the latter will be shifted.

[0044] The heating of the thin layer may further be carried out by thermal spraying techniques, in particular by spraying with a plasma torch (plasma spraying).

[0045] Plasma is an ionized gas, generally obtained by subjecting a gas called "plasmogenic" excitation such as a strong continuous or alternating electric field (for example, an electric arc). Under the action of this excitation, the electrons are pulled out of the gas atoms and the charges formed in this way migrate towards the opposite charge electrodes. Then, these charges excite other gas atoms as a result of an avalanche effect creating a homogeneous or microfilamentary discharge or arc.

Plasmas can be "hot" (the gas is completely ionised and the plasma temperature is in the order of 10)⁶ ° C), or "thermal" (the gas is almost completely ionised and the plasma temperature is in the order of 10)⁴ ° C, e.g. for electric arcs). Plasmas contain many reactive particles, i.e. they can interact with matter with free ions, electrons or radicals. In the case of a plasma torch, the gas is injected through an electric arc, and the thermal plasma generated is inflated towards the substrate to be treated. Plasma torch is commonly used to apply thin layers to various substrates by adding powder precursors to the plasma.

[0046] Within the scope of the invention, the plasma torch is preferably connected to an automatic displacement system arranged perpendicular to the movement of the coated substrate and enabling the entire surface to be treated by successive movement of the torch back and forth above the substrate.

[0047] The injected gas is preferably nitrogen, air or argon, preferably having a volume of hydrogen between 5 and 50%, especially between 15 and 30%.

[0048] Heating of the thin layer can also be carried out by subjecting said thin layer to at least a flame.

[0049] This flame treatment is preferably carried out on a flame treatment board arranged perpendicular to the movement of the substrate. The length of the flame treatment device is preferably at least equal to the width of the coated substrate, which allows ease of processing when moving without the need for a displacement system. The gas used can be a mixture of oxidizing gas, especially selected from air, oxygen or mixtures thereof, and combustible gas, especially selected from natural (natural) gas, propane, butane, and even acetylene or hydrogen, or mixtures thereof. Oxygen is preferred as the oxidizing gas, in particular in combination with natural gas (methane) or propane, on the one hand, because this allows very high temperatures to be achieved and, consequently, shortens the treatment and avoids heating the substrate, and on the other hand, because it allows avoiding the production of oxides nitrogen NOx. To achieve the desired temperatures at the level of the thin layer, the coated substrate is usually placed within the visible flame, especially at the level of the hottest flame zone, the visible portion of the flame then extending around the treated zone.

[0050] Flame treatment is a technique commonly used to treat polymer surfaces to improve their wettability and to facilitate paint coating. In the application that encompasses it, the principle is to subject the surface to be treated with the radicals produced by combustion without applying said surface to a high temperature. Application US 2006/128563 describes the use of this technique for activating the surface of titanium oxide layers to improve their hydrophilic properties. The treatments described, quite similar to those carried out on polymeric substrates, consist of moving the substrate at or slightly below (a few centimeters) the tip of the visible flame. This type of treatment, which aims to form hydroxyl moieties on the surface of titanium oxide, is not suitable, however, for bringing a thin layer of titanium oxide to temperatures above 200 ° C and for increasing the degree of crystallinity of titanium oxide, because the temperatures at the top of the visible flame are insufficient.

[0051] Heating of the thin layer can also be carried out by means of radiation in the microwave range (wavelengths from 1 millimeter to 30 centimeters, or frequencies from 1 to 300 GHz).

[0052] Heating of the thin layer can also be carried out by placing said thin layer in contact with a hot solid or liquid. This can be, for example, a heated rotary shaft in contact with which a thinly coated heating substrate moves. The shaft can be cylindrical or contain many facets, thus allowing an increase in the contact surface between the shaft and the ground. The hot solid, preferably in the form of a roller, is preferably made of a flexible material so that it can adapt to any surface unevenness or deformation of the substrate. It preferably has a high thermal conductivity to achieve adequate heat transfer to the surface of the substrate. The solid is preferably brought to a temperature of at least 500 ° C, even 600 ° C and even 700 ° C.

[0053] Methods of heating by induction and flame treatment are preferred when it is not desirable to use a mechanical displacement device above the substrate. The methods of heating by infrared radiation or induction can be used in a device for applying a magnetron vacuum line. The latter are also advantageous when the consumption of large amounts of gas is not desired.

[0054] In the case of a thin layer based on silver (or consisting of silver), it is preferred to bring said thin layer to a temperature comprised between 300 and 600 ° C, preferably between 350 and 550 ° C. The preferred techniques are heating by means of a laser emitting infrared radiation, by induction, using a plasma torch or by flame treatment.

[0055] In the case of silver-based layers, it has been observed that heating too long or too high intensity, especially with the help of an infrared or induction laser, can not only lead to an increase in the substrate temperature, but also destroy the layer continuity, creating from a primarily continuous layer, a discontinuous layer, containing individual silver clumps, causing blur in direct observation or in strong lighting. This embodiment is obviously not desirable and is not within the scope of the invention.

[0056] The invention also relates to a method for obtaining a material comprising a substrate and at least one thin layer, characterized in that said at least one thin layer is applied to said substrate by cathodic sputtering in a magnetic field, and by subjecting said at least one thin layer heat-treated according to the invention.

[0057] Furthermore, the invention relates to materials that can be obtained by the process of the invention.

[0058] In fact, the method according to the invention makes it possible to obtain thin-layer materials whose degree of crystallinity could only be obtained by thermal treatments of hardening, bending or annealing or other treatments affecting the entire substrate during application. Thus, the materials obtained according to the invention differ from the materials known in the prior art in that they have a different structure, in particular because they do not have in their thickness a stress profile characteristic of the stress profile of tempered glass and / or that they do not cause the same diffusion of (alkaline) elements , oxygen, etc.) from the ground or from the outside.

[0059] Such material consists, for example, of an unhardened glass substrate coated with a thin layer system comprising at least one silver layer with a thickness of e (expressed in nm). The system is characterized by the resistance of the Rc sheet (expressed in ohms) corresponding to the formula:

R_c xe² 120 <25 xe [0060] The resistance of the conductive thin film sheet depends on its thickness according to ₂ Fuchs-Sondheimer's law, which is expressed as Rc xe = pxe + A. In this formula, p denotes the internal resistivity of the thin film forming material, and A corresponds to the mirror or diffuse reflection of charge carriers at the level of the contact surface. The invention makes it possible to obtain an improvement in the internal resistivity p such that p is less than or equal to 25 and an improvement in the reflection of the carriers so that A is less than or equal to 120, preferably 110 and even 105.

[0061] Thus, the method according to the invention makes it possible to obtain layers having very low resistances, which hitherto could not be achieved by means of quenching. However, because the glass is not toughened, it does not show in its thickness the stress profile characteristic of toughened glass (the occurrence of tensile and compressive stresses at the level of two surfaces), and as a consequence it is possible to cut.

[0062] The layer system is preferably of the type described earlier in this text, or in stitching applications WO2007 / 110552, WO2007 / 101964, WO2007 / 101963, WO2007 / 054656, WO2007 / 054655, WO2007 / 042688, WO2007 / 042687, WO2005 / 110939 .

WO2005 / 051858, WO2005 / 019126, WO04 / 043871, WO00 / 24686, WO00 / 29347, EP0995724, EP0995725 WO99 / ​​45415, EP922681, EP894774, EP877006, EP745569, EP718250.

[0063] The substrates obtained according to the invention can be used in straight, composite or laminated glass, mirrors, glass wall coverings. In the case of a composite pane comprising at least two layers of glass separated by a layer of gas, it is preferred that the thin layer is applied to the surface in contact with said layer of gas.

[0064] The invention is illustrated by the following non-limiting embodiments.

EXAMPLE 1 [0065] Sodium-calcium silicate glass substrate obtained by the "float" method and then cut in such a way that its size was 3 m wide 6 m long, coated continuously using a magnetron method thin layer system containing a layer silver, which silver layer gives the glass low emissivity properties.

[0066] This layer system consisted successively (starting from the substrate to the outer surface) of the following layers of oxides, metals or nitrides, with the geometrical thicknesses indicated in brackets:

Glass / SnO₂ (20 nm) / ZnO (15 nm) / Ag (8.5 nm) / Ni-Cr / ZnO (15 nm) / Si₃N₄ (25 nm).

[0067] Between the output from the magnetron line and the storage device, there is a device comprising:

• YAG laser (navy-aluminum-yttrium Y2Al15O2) with an admixture of neodymium emitting continuously or pulsed radiation with a wavelength of 1.09 micrometres focused on a silver layer, with a spot width of about 0.3 to 0.5 mm, and • quick laser system (3 to 5 meters per second) in a direction perpendicular to the direction of the substrate.

[0068] The temperature of the glass substrate during processing did not exceed 50 ° C, as measured by pyrometry at the surface level of the substrate opposite to the surface on which the thin film coating is located.

[0069] Table 1 below indicates the change in the following properties after treatment:

• light transmission using the D65 illuminant, calculated from the experimental spectrum, taking as reference the D65 light standard and the «CIE 1964» colorimetric observer for a double-glazed unit with 4 mm thick glass plates and a gas layer (a mixture of 90% argon and 10 % air) is 16 mm thick, permeability is marked as "TL" and expressed as a percentage, • sheet resistance, marked as Rc and expressed in ohms, • normal emissivity at 283 K calculated in accordance with EN 12898 from the reflection spectrum in the spectral range of 5 - 50 microns, marked as ε n, and expressed as a percentage.

[0070] The latter two properties (sheet resistance and emissivity), which illustrate the results of the electrical conductivity and low emissivity of the layer, reflect the degree of crystallinity and size of the crystals of the silver layer, since the more crystallized silver layers simultaneously have greater electrical conductivity and better emissivity properties.

Table 1

<td colspan="2">TL (%)</td><td colspan="2">Rc (Ω)</td><td colspan="2">εη (%)</td>

<td>in front of</td><td>P^about</td><td>In front of</td><td>P^about</td><td>In front of</td><td>P^about</td>

<td> 77,0</td><td> 78,3</td><td> 5,0</td><td> 4,5</td><td> 5,5</td><td> 5,0</td>

[0071] The changes caused by the treatment in terms of sheet resistance and normal emissivity are in the order of 10%. These results show that treating the layer system (and especially treating the silver layer) with an infrared laser, resulted in improved crystallization of the silver layer, characterized in particular by a stronger degree of crystallization and a larger size of crystals. In addition, a significant increase in the light transmission of the resulting pane can be seen.

EXAMPLE 2 [0072] In this example, an identical coated substrate was used as in Example 1, thus coated with a layer system comprising a silver layer.

[0073] The method of heating was induction, implemented by means of an inductor whose geometry is specially adapted to the processing of flat surfaces. The frequency was 2 MHz, power may vary around a few kW.

[0074] The temperature of the glass substrate during the treatment, which lasted only a few seconds, did not exceed 150 ° C.

[0075] Table 2 below indicates the change in properties described in the example case

2.

Table 2

<td colspan="2">TL (%)</td><td colspan="2">Rc (Ω)</td><td colspan="2">εη (%)</td>

<td>in front of</td><td>P^about</td><td>in front of</td><td>P^about</td><td>in front of</td><td>P^about</td>

<td> 76,9</td><td> 77,5</td><td> 5,0</td><td> 4,6</td><td> 5,5</td><td> 5,1</td>

[0076] Changes in sheet resistance and emissivity, quite comparable to those caused by laser treatment emitting infrared radiation, further show an increase in the degree of crystallization of the silver layer.

EXAMPLE 3 [0077] The substrate identical to the one treated with Examples 1 and 2, in this example was subjected to heating carried out by means of a plasma torch. The plasmogenic gas was a 4: 1 mixture of argon or nitrogen with hydrogen.

[0078] A plasma torch with a power of 25 to 40 kW was mounted on the rapid moving device (of the order of 1 to 4 meters per second) in a direction perpendicular to the direction of the substrate. The width of the zone subjected to the plasma torch was about 3 to 10 mm.

[0079] The temperature of the glass substrate during processing did not exceed 90 ° C.

[0080] Table 3 below shows the changes resulting from heating in terms of light transmission, sheet resistance and normal emissivity.

Table 3

<td colspan="2">TL (%)</td><td colspan="2">Rc (Ω)</td><td colspan="2">εη (%)</td>

<td>in front of</td><td>P^about</td><td>in front of</td><td>P^about</td><td>in front of</td><td>P^about</td>

<td> 77,0</td><td> 78,5</td><td> 5,0</td><td> 4,4</td><td> 5,5</td><td> 4,9</td>

[0081] Table 4 below lists the same properties, but for the layer system in which the silver layer is 15 nm thick.

Table 4

<td colspan="2">TL (%)</td><td colspan="2">Rc (Ω)</td><td colspan="2">εn (%)</td>

<td>in front of</td><td>p^about</td><td>in front of</td><td>p^about</td><td>in front of</td><td>p^about</td>

<td> 71,0</td><td> 72,0</td><td> 2,2</td><td> 2,0</td><td> 2,4</td><td> 2,2</td>

[0082] As with Examples 2 and 3, heating resulted in improved properties that are indicative of better crystallization of the silver layer.

EXAMPLE 4 [0083] The same coated substrate as the one treated in Examples 1, 2 and 3, in this example was subjected to flame heating. The combustible material was propane and the oxidant was air. Getting oxygen also allows good results.

[0084] The coated substrate, after application in a magnetron deposition chamber, moved at a constant speed under a stationary flame treatment deck, whose width was greater than or equal to the width of the substrate, the latter sliding under the deck at a speed comprised between 2 and 10 meters / minute. The treatment layer was placed at the level of the hottest flame zone.

[0085] The temperature of the glass substrate during processing, however, did not exceed 100 ° C.

[0086] Table 5 below also shows the beneficial development of silver layer crystallization.

Table 5

<td colspan="2">TL (%)</td><td colspan="2">Rc (Ω)</td><td colspan="2">εn (%)</td>

<td>in front of</td><td>P^about</td><td>in front of</td><td>p^about</td><td>in front of</td><td>p^about</td>

<td> 77,0</td><td> 78,2</td><td> 5,1</td><td> 4,5</td><td> 5,6</td><td> 5,0</td>

EXAMPLE 5 (comparative) [0087] The substrate coated with a layer system comprising a silver layer as described in Examples 1, 2, 3 and 4, but in which the thickness of the silver layer was 9 nm, moved after application under a series of infrared radiation emitting lamps distinguishing between layers and substrate.

₂ [0088] The lamp power was about 150 kW / m and the wavelength of the emitted radiation was between 1 and 3 micrometers.

[0089] Table 6 below shows that heating with lamps substantially improves the crystallization of silver layers.

[0090] However, the substrate temperature at the level of the surface opposite to the surface on which the layer system is located exceeds 300 ° C during processing, causing damage to most of the treated glass plates.

Table 6

<td colspan="2">TL (%)</td><td colspan="2">Rc (Ω)</td><td colspan="2">εn (%)</td>

<td>in front of</td><td>p^about</td><td>in front of</td><td>p^about</td><td>in front of</td><td>p^about</td>

<td> 77,2</td><td> 78,5</td><td> 4,6</td><td> 3,8</td><td> 5,1</td><td> 4,3</td>